Method and device for coating the junction area between at least two elongated elements, in particular between electric cables

ABSTRACT

A method of coating the junction area between elongated elements, in particular between electric cables. This method includes the steps of: arranging a rigid tubular support having two axially separable tubular halves; mounting an elastic tubular sleeve in an elastically radially expanded condition on an outer surface of the support; interposing a lubricating material between the support and sleeve; arranging a circumferentially continuous sealing element between the halves to prevent the lubricant from percolating between the halves; positioning the support around the junction area; and moving the halves apart from each other to enable the sleeve to collapse on the junction area. A device for coating the junction area between elongated elements and a method of making the device and a joint for electric cables.

CROSS REFERENCE TO RELATED APPLICATION

This application is a national phase application based onPCT/IB2004/003523, filed Oct. 27,2004, the content of all of which isincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and a device for coating thejunction area between at least two elongated elements. In particular,the present invention relates to a method and a device for coating thejunction area between at least two elongated elements by application ofan elastic tubular sleeve.

In more detail, the present invention relates to a method and a devicefor coating the junction area between two electric cables.

It is a further object of the present invention to provide a joint forelectric cables comprising a device for coating the junction areabetween said cables.

2. Description of the Related Art

In the specific case of junctions between electric cables, the device ofthe invention can be used for low-, medium- or high-voltage cables.Preferably, this device is used for coating the junction area betweenmedium- and high-voltage cables.

Generally, application of an elastic tubular sleeve in the junction areabetween two elongated elements is obtained by use of a rigid tubularsupport that can be preferably separated into two halves, on which thesleeve is positioned in a radially expanded condition.

The sleeve expanded on said support is first fitted on one end of one ofthe elongated elements and, once junction of said elongated elements orof part of the constituent elements thereof has been carried out, thesupport is caused to slide on the elongated element until bringing thesleeve in register with the junction area itself.

In the preferred case in which the support consists of two halves, oncethe sleeve is positioned at the junction area, the two halves arereleased from each other and axially moved apart so as to enable thesleeve to adhere to the underlying elongated elements at the junctionarea of same.

The two halves, before separating and moving apart from each other, canbe maintained in mutual engagement through different typologies ofconstraints or links.

For example, the European Patent EP 917,269 shows a “trigger” connectionin which a toothed ring, made at one end of a first half, engages acorresponding circumferential groove made at the axially faced end of asecond half.

To facilitate mutual separation of the two halves, use of auxiliaryelongated elements is provided, each of which has a first portionextending along the outer surface of one half and inserted between saidhalf and the sleeve fitted thereon, and a second portion, contiguous tothe first one that, stepping over the end profile of said half, axiallyextends within the half itself, afterwards projecting at least partlyfrom the axially opposite end.

The above mentioned European patent further describes a mutualengagement between the halves that is obtained through a circumferentialweakening line defined by through holes of different sizes.

An alternative structure facilitating removal of the two halves isdescribed in the European Patent EP 541,000 and the U.S. Pat. No.6,472,600 both in the name of the same Applicant, according to whicheach half has a continuous helical cut defining a spiralled tape that isgradually removed by the operator by exerting a pulling action on thetape itself or on grip elements connected with said tape, said tape orgrip elements such projecting from the outer end of each half thatgradual removal of the support (and consequent collapsing of the sleeveon the junction area) is carried out starting from the centre of thejunction area.

In said U.S. Pat. No. 6,472,600 it is further contemplated that one ofthe two halves be provided, at one of its ends, with a plurality ofprotuberances extending in an inclined direction relative to thelongitudinal axis of the support, whereas the other half has a pluralityof corresponding recesses matching the shape of said protuberances.

In this way the two halves are maintained in mutual engagement, forminga single piece until the moment the sleeve, that is disposed in anexpanded condition on the corresponding support, is positioned at thejunction area. Subsequently, at the moment said halves must beseparated, it is required that one half be rotated relative to the otheraround its longitudinal axis to disengage the above mentionedprotuberances from the respective recesses.

A further embodiment described in said US patent consists in providing afrangible ring for connection between the two support halves, said ringbeing obtained through formation of through slits or welding points. Incompliance with this embodiment, separation of the two halves isachieved by use of a string fastened to the ring itself and pulling ofwhich by the operator triggers breaking of said ring thereby causingmutual moving away of said halves in an axial direction.

In order to promote mutual moving apart of the two halves, and inparticular sliding of the halves relative to the sleeve, use of alubricating material interposed between the support and sleeve may beprovided. This lubricating material is applied at the moment the sleeveis positioned on the support in an expanded condition.

The Applicant could ascertain that the technical solutions adopted inthe known art to link the two support halves together are not able toensure that the lubricating material will remain correctly positionedbetween the support and sleeve until the sleeve is applied onto thejunction area. In fact it is to be noted that generally betweenmanufacturing of the junction device and use of said device medium-longperiods of time even in the order of some months may elapse.

In particular, the Applicant has ascertained that if a supportpreviously made up of two parts or separable into two halves at themoment of being extracted, is wished to be used, the solutions known inthe art contemplate circumferential discontinuities causing percolationof the lubricant through the faced surfaces of the two halves so that,as a result, the lubricant is no longer in the region where it had beenoriginally applied.

Lack of lubrication, even if partial, during the support-ejection steprepresents an important problem because it causes an unacceptableincrease in the ejection times and can even involve stopping of saidstep.

SUMMARY OF THE INVENTION

The Applicant therefore has become aware of the fact that, in order toensure an efficient lubricating action of the contact surface betweenthe sleeve and the support, at the moment said support is arranged at ajunction area between two elongated elements, it is necessary to ensurea uniform and homogeneous distribution of the lubricating material atthe sleeve-support interface, without the occurrence of undesirablemigrations and percolations of the lubricating material itself at thecoupling region between the two halves constituting the support itself,also in the presence of particularly prolonged storage times.

The Applicant has found that this problem can be advantageously resolvedby arranging a circumferentially continuous annular sealing elementbetween the two support halves, which element is able, on the one hand,to prevent the lubricating material from percolating between the twohalves and, on the other hand, to allow easy mutual disassembling ofsaid halves.

In particular, it is an aim of the present invention to provide a methodof coating the junction area between at least two elongated elements, inparticular between electric cables, comprising the following steps:setting a rigid tubular support consisting of two axially separabletubular halves, arranging a circumferentially continuous annular sealingelement between said halves; mounting an elastic tubular sleeve in anelastically radially expanded condition on an outer surface of saidsupport; interposing a lubricating material between said support andsleeve; positioning said support provided with said sleeve around saidjunction area; moving said halves away from each other to enablecollapsing of said elastic tubular sleeve on said junction area.

Another aim of the present invention consists in providing a device forcoating the junction area between at least two elongated elements, inparticular between electric cables, comprising: a rigid tubular supportconsisting of two tubular axially separable halves; an elastic tubularsleeve mounted, in an elastically radially expanded condition, on anouter surface of said support; a lubricating material interposed betweensaid support and sleeve; a circumferentially continuous annular sealingelement interposed between said halves to prevent said lubricant frompercolating between said halves.

It is a further aim of the present invention to provide a joint forelectric cables comprising: a rigid tubular support consisting of twotubular axially separable halves; an elastic tubular sleeve mounted, inan elastically radially expanded condition, on an outer surface of saidsupport and comprising at least one electrical-insulation layer; alubricating material interposed between said support and sleeve; acircumferentially continuous annular sealing element interposed betweensaid halves to prevent said lubricant from percolating between thehalves themselves.

Further features and advantages will become more apparent from thedetailed description of a preferred but not exclusive embodiment of amethod and a device for coating the junction area between at least twoelongated elements, in particular between electric cables, as well as ofa joint for electric cables in accordance with the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

This description will be set out hereinafter with reference to theaccompanying drawings, given by way of non-limiting example, in which:

FIG. 1 is a partial longitudinal section view of a first embodiment of adevice in accordance with the invention;

FIG. 2 is a partial longitudinal section view of a second embodiment ofa device in accordance with the invention;

FIGS. 3 a-3 e show the operating steps of the method of coating thejunction area between two elongated elements in accordance with theinvention;

FIG. 4 is a diagrammatic perspective view of a support of the device inFIG. 1;

FIG. 5 a is a partial longitudinal section view of a third embodiment ofa support being part of the junction device of the invention;

FIG. 5 b is a partial longitudinal section view of a fourth embodimentof a support being part of the junction device of the invention;

FIG. 6 is a diagrammatic perspective view of the devices shown in FIGS.5 a and 5 b;

FIG. 7 is a partial side view of a support being part of the junctiondevice shown in FIG. 6;

FIG. 8 is a partial longitudinal section view of a joint for electriccables in accordance with the invention.

With reference to the drawings, a junction device in accordance with theinvention to coat the junction area between at least two elongatedelements has been generally identified with reference numeral 1.

In compliance with the invention, the above mentioned elongated elementscan be selected among electric cables, pipelines, electric terminals andpossible combinations thereof, for example.

DETAILED DESCRIPTION OF THE INVENTION

The elongated elements, denoted at 61, 62 are only shown in FIGS. 3 a-3e, for the sake of clarity.

The junction area 60 between the elongated elements 61, 62 can consistboth of the area where two electric cables or two pipelines are mutuallyengaged, and of the connection area between a cable and a respectiveelectric terminal.

Device 1 (see FIG. 1, in particular) comprises a rigid tubular support10 adapted to be axially separated into two tubular halves 11. 12.

Support 10 can be made of a rigid plastic material such as polyethylene,propylene or polyvinylchloride, for example. Halves 11, 12 can have acylindrical conformation. Alternatively, halves 11, 12 have afrustoconical conformation. In the last-mentioned case halves 11, 12axially face themselves at their minor bases.

Fitted at the radially outer surface of support 10 is an elastic tubularsleeve 20 in a condition of radial elastic expansion.

Advantageously, sleeve 20 is positioned on both halves 11, 12 at thefacing region thereof. Preferably, sleeve 20 is symmetrically disposedrelative to said facing region of said halves.

Sleeve 20 is a cold-shrinkable sleeve, i.e. it is able to collapse onthe junction area by virtue of the elastic properties of the materialsof which it is made.

Depending on the applications for which it is designed (as a protectionfor the junction area between two pipelines or between two electriccables, for example), sleeve 20 can be made of different materials. Theinstance of a sleeve 20 set to be used for coating and protecting thejunction area between two electric cables will be analysed herebelow.

Interposed between the support 10 and sleeve 20 is a lubricatingmaterial 30 that, as better explained in the following, facilitatesmutual moving away of halves 11, 12 of the support 10 and consequentapplication of sleeve 20 to the junction area 60. The lubricatingmaterial 30 can be oil or grease. Preferably, lubricant 30 is asilicone-base grease or a polyalkylenglycol-base grease, advantageouslywith addition of a filler comprising talc in a proportion of 15-35% byweight for example, and preferably containing at least an additivecapable of giving said grease a resistance to pressure. Preferably, saidadditive is boron nitride. Preferably, said additive is in a proportionof 2 to 10% by weight.

The used grease is such selected that it does not flow away from thejunction area following the hooping force exerted by the elastic sleeve20 during the storage period of device 1, which period can be includedjust as an indication, between six months and three years.

In addition, the used grease must form a continuous lubricating layerover the whole outer surface 10 a of support 10, in spite of thepressure exerted on sleeve 20. This pressure can be included between 5-6bars (5×10⁵-6×10⁵ Pa) and even reach higher values, until about 15 bars(15×10⁵ Pa) for example.

In compliance with the present invention, a circumferentially continuoussealing element 40 is provided between the first and second halves 11,12 which will be able, on the one hand, to allow separation andsubsequent moving away of the two halves once the tubular sleeve hasbeen positioned at the junction area, and on the other hand, to preventthe lubricant 30 from percolating between said halves 11, 12.

Preferably, the sealing element 40 is made of one piece with at leastone of the halves 11, 12 of support 10. In particular, in compliancewith the first embodiment shown in FIG. 1 and the second embodimentshown in FIG. 2, the sealing element 40 is made of one piece with bothhalves 11, 12 and is substantially coaxial with said halves.

In more detail, in the first embodiment shown in FIG. 1 the innerdiameter d3 of the sealing element 40 is substantially the same as theinner diameter d4 of support 10, whereas the outer diameter d1 of thesealing element 40 is smaller than the outer diameter d2 of support 10.

In accordance with this embodiment, the sealing element 40 isadvantageously obtained through formation of a groove 13 in the outersurface 10 a of support 10, this groove 13 defining the above mentionedtwo distinct halves 11, 12.

The residual thickness at groove 13 (given by the difference between d1and d3) defines said circumferentially continuous sealing element 40 ofthe junction device in accordance with the invention.

In a second embodiment shown in FIG. 2, groove 13 is formed in the innersurface 10 b of support 10. In this case, the inner diameter d3 of thesealing element 40 is bigger than the inner diameter d4 of support 10,and the outer diameter d1 of the sealing element 40 is substantially thesame as the outer diameter d2 of support 10.

The residual thickness at groove 13, given by the difference between theouter diameter d1 and inner diameter d3 of the sealing element 40,defines the circumferentially continuous sealing element 40 of thejunction device in accordance with the invention.

The residual thickness is preferably included between 0.05 mm and 0.5mm. More preferably, the residual thickness is 0.1 mm.

Advantageously, sleeve 20 is positioned at the groove 13; preferably,said sleeve is axially centred relative to said groove 13.

In a third embodiment (shown in FIG. 5 a) and a fourth embodiment (shownin FIG. 5 b), the sealing element 40 comprises a first portion 41 and asecond portion 42. More particularly, the first portion 41 is made ofone piece with the first half 11 of support 10 and the second portion 42is made of one piece with the second half 12. Said first and secondportions 41, 42 of the sealing element 40 axially face each other toform a labyrinth profile preventing percolation of the lubricant 30between portions 41, 42 and therefore between halves 11, 12.

To the aims of the present description, the expression “labyrinthprofile” means any non-rectilinear profile formed in the thickness ofthe support 10 and adapted to determine a tortuous path capable ofrestricting or preventing flowing of a fluid along the path itself.

In compliance with the present invention, this profile can have an atleast partly curvilinear conformation.

Alternatively, this profile is provided with a plurality of portions todefine a broken line.

The labyrinth profile as above defined allows one or moreprotuberances/recesses to be set that are able to substantially preventor restrict migration of lubricant 30 to the sleeve/support interface.

For example, as shown in FIG. 5 a, the first portion 41 of the sealingelement 40 has a circumferentially continuous protuberance 41 aprojecting from an axial end 11 a of the first half 11, whereas thesecond portion 42 has a circumferentially continuous cavity 42 a formedat an axial end 12 a of the second half 12.

Protuberance 41 a and cavity 42 a suitably conform in shape to define amutual engagement between the first and second halves 11, 12. Accordingto this embodiment the labyrinth profile consists of a broken line.

Shown in FIG. 5 b is a further embodiment of said labyrinth profileaccording to which, at the protuberance 41 a and the cavity 42 b, theprofile has a substantially curvilinear conformation.

For the purpose of making the drawings simpler and clearer, theelongated elements joined to each other are not shown in FIGS. 5 a and 5b, neither shown is sleeve 20 positioned at the contact surface betweenthe portions 41, 42 of the sealing element 40.

Should the sealing element 40 consist of the two portions 41, 42 made ofone piece with the first and second halves 11, 12 of support 10respectively, the junction device 1 would be conveniently provided withpulling elements 50 (FIG. 6) exerting a suitable axial force on the twohalves 11, 12 capable of maintaining portions 41, 42 in a condition ofmutual axial contact.

These pulling elements 50, preferably made in the form of ribbonelements of polypropylene, polyesters or metal, are linked to axiallyopposite ends of halves 11, 12 and prevent the latter from moving awayfrom each other thereby starting the shrinkage step of the sleeve beforethe junction device is correctly disposed at the junction area of theelongated elements 61, 62.

In particular, these pulling elements 50 exert a constraint on halves11, 12 to such an extent that the axial force of mutual approach exertedon said halves 11, 12 is greater than the axial component of the elasticshrinkage force exerted by sleeve 20 on support 10.

In other words, the pulling elements 50 are submitted to a tensionpreferably included between about 30 N and about 200 N, more preferablyincluded between about 60 N and about 100 N.

The junction device hitherto described lends itself to be used forputting into practice a method of coating the junction area between atleast two elongated elements in accordance with the present invention.

In compliance with the invention, this method the operating sequence ofwhich is diagrammatically shown in FIGS. 3 a-3 e, contemplates thestarting step of inserting the junction device 1 around one of theelongated elements 61, 62 to be joined and positioning this device in anon-operating condition on said element until the junction operation hasbeen carried out.

In more detail, as shown in FIG. 3 a, device 1 is fitted around theelongated element 62 in such a manner that the end 62 a of saidelongated element 62 axially projects from support 10 and is thereforeavailable for the operator so that it can perform the junctionoperation. Diagrammatically shown in FIG. 3 b is the junction stepbetween said two elongated elements 61, 62.

When the junction operation has been completed, there is a step ofmaking device 1 axially slide along the elongated element 62 untilbringing sleeve 20 close to the junction area 60, as shown in FIG. 3 c.

Once device 1 is correctly positioned, the two halves 11, 12 are axiallymoved apart from each other so as to enable the elastic shrinkage ofsleeve 20 at the junction area 60.

At this point depending on the type of support used, the moving-apartstep in accordance with the method of the present invention can beperformed following different operating modes.

For instance, if the first or second embodiments shown in FIGS. 1 and 2respectively are used, the operator exerts a bending force on support 10so as to start breaking of the weakened region of the support 10 definedby the sealing element 40, and therefore enable separation of the twohalves 11, 12. Preferably, this bending force is applied by the operatorclose to the axial ends of support 10. Advantageously, this bendingforce is exerted in at least two different application directions so asto carry out full breaking of said weakened region.

If, on the contrary, the third or fourth embodiments shown in FIGS. 5 aand 5 b respectively are used, the method in accordance with theinvention contemplates the step of disengaging the pulling elements 50from halves 11, 12 (by cutting said pulling elements 50, for example) sothat the elastic shrinkage of sleeve 20 on support 10 causes aprogressive ejection of the two halves 11, 12 out of the junction area60.

If halves 11, 12 of support 10 have a frustoconical conformation (asshown in FIG. 7), this ejecting action is advantageously backed up bythe geometry of said halves.

If, on the contrary, halves 11, 12 have a cylindrical conformation,exerting an initial bending force on said halves may berequired—preferably at the facing region of the latter—in order to startseparation of the two halves 11, 12 and enable collapsing of sleeve 20on the junction area 60. The hooping action due to the elastic shrinkageforce of sleeve 20 on support 10 enables mutual moving apart of halves11, 12 from the junction area to be completed, once the ejection processhas been triggered, without any further application of said pullingforce being necessary.

Once halves 11, 12 have been ejected (see FIG. 3 e), they are removedfrom the welded elongated elements 61, 62 by any operation suitable forthe purpose, through cutting of said halves for example.

As above mentioned, in a particular application scope of the presentinvention each of the elongated elements 61, 62 is represented by anelectric cable.

Shown in FIG. 8 is a joint 70 according to the present invention, saidjoint comprising the junction device 1 as above described for carryingout junction between two high voltage electric cables 61, 62.

In the present description the term “medium voltage” means a voltagetypically included between about 1 kV and about 30 kV, whereas the term“high voltage” means a voltage typically higher than about 30 kV.

As shown in FIG. 8, cables 61 and 62, starting from a radially internalposition towards a radially external position, are provided respectivelyof: a metal conductor 71, 72; an inner semi-conductive layer (notshown); an insulating layer 73, 74; an outer semi-conductive layer 75,76. The assembly of these elements is generally referred to as cable“core”.

Preferably, conductors 71, 72 are made up of at least two metallic wirestwisted with each other. Alternatively, said conductors are in the formof a solid rod. Preferably, conductors are made of copper or aluminium.

To the aims of the present description, the term “electric insulationmaterial” is used to indicate a material having a dielectric strength ofat least 5 kV/mm, preferably higher than 10 kV/mm. For high-voltagecables, preferably said material has a dielectric strength higher than20 kV/mm, preferably between 20 and 50 kV/mm.

Typically, the insulating layers 73, 74 have a relative dielectricconstant at least as high as 2, preferably included between 2 and 5.

Preferably, the insulating layers 73, 74 are made of a polyolefin-basecross-linked polymer, in particular cross-linked polyethylene (XLPE), orof cross-linked ethylene/propylene copolymers (EPR) orethylene/propylene/diene copolymers (EPDM).

Alternatively, said insulating layers 73, 74 are made of a thermoplasticmaterial comprising a thermoplastic polymer, preferably a polyolefin(such as polyethylene or polypropylene), and a predetermined amount of adielectric liquid, preferably a synthetic oil (such as an aromatic,paraffinic, naphthenic oil).

The inner semi-conductive layers (not shown) and outer semi-conductivelayers 75, 76 are generally obtained by extrusion of a polymer-basematerial, a polyolefin for example (such as polyethylene) to whichconductive carbon black is added so as to give the polymeric base thedesired semi-conductive properties.

At a radially external position to said core, cables 61 and 62 areprovided with a metal screen (not shown) generally made of aluminium,copper or lead.

The metal screen can consist of, for example, a plurality of wires ormetal tapes helically wound around the cable core. Alternatively, themetal screen can consist of a circumferentially continuous tube,obtained starting, for example, from a metal sheet longitudinally bentto obtain a tubular conformation by welding or gluing of the side edgesthereof.

The electric cables 61 and 62 further comprise an outer sheath of apolymer material 77, 78 placed in a radially external position withrespect to the metal screen.

The outher sheath 77,78 is preferably made of polymer material,polyvinylchloride (PVC) or polyethylene (PE) for example, performing thefunction of protecting the cable core from the surrounding environment.

In FIG. 8 the junction area between two electric cables 61, 62 isgenerally denoted at 60 and is obtained by welding of the conductors 71,72 of said cables, for example.

In FIG. 8 the joint 70 is shown fitted at the junction region 60 and hasthe function of restoring continuity of the insulating layers 73, 74 andthe outer semi-conductive layers 75, 76. Therefore, joint 70 comprises aplurality of elements that are radially superposed in coaxialrelationship and that correspond to the constituent elements of thecable.

In detail, joint 70 comprises the support 10, susceptible of beingdivided into the two halves 11, 12 (as above said), and the tubularsleeve 20 fitted on said support in an elastically radially expandedcondition. For more simplicity in description, the lubricating material30 interposed between the support 10 and sleeve 20 is not represented inFIG. 8.

In order to restore the electrical and mechanical continuity of cables61 and 62, sleeve 20 starting from the radially innermost position tothe radially outermost position, comprises:

-   -   a first semi-conductive element 79 (generally referred to as        “electrode”), disposed around support 10 and substantially        extending in a central position of sleeve 20, at the junction        area 60;    -   two second semi-conductive elements 80, 81 (generally referred        to as “baffles”) disposed around support 10 and at the axially        opposite ends of the first semi-conductive element 79;    -   an electric-insulation layer 82, surrounding the first        semi-conductive element 79 and the second semi-conductive        elements 80, 81; and    -   a third semi-conductive element 83 to form a layer disposed at a        radially external position relative to the electric-insulation        layer 82, said third semi-conductive element 83 being designed        (once support 10 has been removed) to connect the outer        semi-conductive layers 75, 76 of cables 61, 62.

The electrode 79 is a voltage-distributing element that is positioned atthe joined ends of the cables and partly overlaps the insulating layersof said cables.

The electrode is made of an electrically semi-conductive material andgenerates a constant-potential Faraday cage cancelling out the effectsdue to the presence of air and any shape unevenness present in theconnecting region of conductors 71, 72.

Baffles 80, 81 have the function of making the distribution of the fluxlines of the electric field uniform at the interruption of the outersemi-conductive layers of the cables. In detail, each baffle consists ofa shield for control of the electric field and is positioned at theaxial ends of the insulating layer.

According to a preferred embodiment, the axial ends of the thirdsemi-conductive element 83 are preferably provided with a lip 84, 85disposed at the axially external ends of the second semi-conductiveelements 80, 81 and in contact with the support 10.

Shown in FIG. 8 is a step of the method in accordance with the inventionin which halves 11, 12 are already decoupled and partly axially movedapart from each other, while sleeve 20 is collapsing on the junctionarea 60.

The method in accordance with the invention further comprises the stepof restoring the metal screens and outer sheaths 77, 78 of the twocables 61, 62.

The metal screens can be restored by for example applying a tubularmetal plait connecting the metal screen of cable 61 with the metalscreen of cable 62. Preferably, the electric continuity between saidmetal screens is completed by superposing said tubular plait on saidscreens and applying a hooping element at said superposition region.Preferably, the hooping element is a metal clamp. More preferably, saidhooping element is a metal spring.

The outer sheath (not shown) can be restored by providing a furtherelastic tubular sleeve (in a radially expanded condition) fitted on afurther support that is disposed on an end of one of the two cables 61,62. Subsequently, once sleeve 20 has been set around the junction area60 and the metal screen has been restored, said further sleeve (i.e. theouter sheath), fitted on said further support, is disposed at thejunction area 60 and collapsing thereof takes place by ejection of saidfurther support.

Alternatively, above all if junction of two medium-voltage electriccables is to be carried out, the metal screen and outer sheath can beintended as constituent elements of sleeve 20.

The invention claimed is:
 1. A method of joining at least two elongatedelements, comprising the steps of: arranging a rigid tubular supporthaving two axially separable tubular halves; arranging acircumferentially-continuous annular sealing element between saidhalves, the circumferentially-continuous annular sealing elementcomprising at least a first portion made integral with at least one ofthe two axially separable tubular halves; mounting an elastic tubularsleeve in an elastically radially expanded condition on an outer surfaceof said support; interposing a lubricating material between said supportand sleeve; positioning said support provided with said sleeve aroundsaid junction area; and mutually moving said halves apart to enable saidelastic tubular sleeve to collapse on said junction area.
 2. The methodas claimed in claim 1, further comprising the step of joiningcorresponding ends of said at least two elongated elements together. 3.The method as claimed in claim 2, wherein said step of joining the endsof the elongated elements together is performed before the step ofpositioning said support.
 4. The method as claimed in claim 2, furthercomprising the step of axially inserting one of said elongated elementsin said support so that the end of said elongated element axiallyprojects from said support.
 5. The method as claimed in claim 4, whereinsaid step of axially inserting said elongated element in said support isperformed before joining the ends of said elongated elements together.